Although there are ways that cloning is useful for, there are also downsides to cloning. Like some people think that we shouldn’t clone because we are going against Mother Nature. There are other bad things to cloning, like it could also clone undesirable traits, or it will invite malpractices from doctors or in society. Also technical and economic barriers will have to be considered, and if the cloned organs will be cost effective. Also if we clone too much we run the risk of have a society that is all the same. There is also the risk of transferring disease between transgenic animals and the animal form which the trasgenes were derived. There is also the fact that cloning may cause people to settle for the best existing animals, not allowing for improvement of the species. That is some of the main reasons on why cloning is bad.
Links
http://library.thinkquest.org/24355/data/reactions/cons.html
http://www.buzzle.com/articles/pros-and-cons-of-cloning.